getCookies

addHeader

If there was no entry for that header name before, the value will be used
as-is. In case of an existing entry, a String array will be created,
adding the given value (more specifically, its toString representation)
as further element.

Multiple values can only be stored as list of Strings, following the
Servlet spec (see getHeaders accessor). As alternative to
repeated addHeader calls for individual elements, you can
use a single call with an entire array or Collection of values as
parameter.